1. Field of the Invention
The present invention relates to a power control device for a signal with optimized input dynamics. The device according to the invention enables automatic gain control of the power control device. It is applied, for example, to the signal reception channel in a satellite geopositioning device.
2. Discussion on the Background
An automatic gain control device, notably used in a radio transmission or reception channel, enables adjustment of the amplification gain of the input signal in such a way as to obtain an acceptable signal level at the channel output, independently of the power of the input signal. This enables presentation to the circuit located at the end of the transmission or reception channel of a signal whose power is optimum for guaranteeing the expected performance of the transmission/reception channel.
Devices such as, for example, channels for the reception of signals originating from satellites, which are fitted to geopositioning devices such as GPS (“Global Positioning System”) receivers, operate under high input dynamics, with extremely low-power signals. It must be noted here that signals with high input dynamics are signals in which the difference between the highest levels and the lowest levels is great. In devices of this type, it is necessary to minimize the interference caused by any non-linearity of the system in order to be able to ensure acceptable sensitivity. The system therefore requires a function whose performance is constant across the entire input dynamic range. Moreover, for applications with very low consumption, it is necessary to ensure that the automatic gain control minimizes consumption.
Solutions currently exist which consist in utilizing functions which reduce the output dynamics at the same time as the gain, as these functions present constant input dynamics. Solutions of this type assume that, the higher the power of the input signal, the more the automatic gain control function reduces, thereby lowering the output compression, i.e. reducing the ratio between the highest and lowest levels. The power of the output signal then becomes inconsistent with the power of the signal to be processed. To overcome this problem, some solutions consist in overdimensioning the compression of the input stage, which adversely affects consumption.
Other solutions exist which use counter-reaction systems on the transmitters, which adversely affects the noise factor.
All of the aforementioned solutions are incompatible with the low-consumption constraint, and are rarely compatible with a low-voltage power supply.